1. Field of the Invention
The present invention relates to a fiber-optic test probe and a connector adapter for testing fiber-optic terminations for example, in fiber optic connector assemblies and, in particular, to a fiber-optic test probe and connector adapter that provides relatively precise axial alignment of the test probe relative to the mating terminus to be tested. The test probe includes a compression spring which preloads the terminus of the test probe against the terminus to be tested in order to minimize the air gap therebetween thereby minimizing transmission losses, such as Fresnel reflection losses and improving performance of the test system.
2. Description of the Prior Art
Fiber-optic systems are used in many applications to transmit analog and digital data signals. For example, fiber-optic systems are used in high-speed data communications and telecommunications, in part, because of their insensitivity to electromagnetic interference. Because of the relatively small size, light weight and immunity to electromagnetic interference, fiber-optic systems are known to be used in various applications including automobiles, aircraft and ships.
Terminations of fiber-optic cables require precise axial alignment of the optic fibers to avoid reflection and refraction of the light in order to avoid errors and distortions of the optical output signals. Various multi-channel optical systems are known. Such multiple channel optical systems utilize multiple optical fibers terminated to optical connectors. Various methods are known for testing the terminations of the optical fibers within the optical connectors, as shown in FIGS. 1, 2 and 3.
FIG. 1 illustrates a known optical connector, identified with the reference numeral 20. The optical connector 20 is a four-channel device used to terminate four optical fibers. The optical connector 20 includes a socket insert 22 with axial bores 24 in which the optical fibers are terminated to contacts or termini. Each of the optical fibers terminated in the optical connector 20 are tested individually by inserting a mating like terminus 26 into its respective axial bore 24. The mating terminus 26 includes a terminated fiber (not shown) for contacting an opposing terminus in the optical connector to be tested. The mating terminus 26 is connected by way of a simplex cable 27 to test equipment (not shown).
Although such a method provides a relatively cost-effective method to test the terminations of the optical fibers within the optical connector 20, the terminus is subject to radial loads (i.e. loads or components of loads generally perpendicular to the axis of the terminus in the probe), which can affect the axial alignment of the test terminus 26 relative to the terminus within the optical connector 20 to be tested. Should the test terminus 26 become even slightly axially misaligned with the terminus in the optical connector 20, reflection and refraction of the light will result in losses and thus inaccurate measurements.
Another known method for testing optical fibers terminated in an optical connector is illustrated in FIG. 2. With this method a mating connector is utilized with opposite style interfacing termini. Although such a method provides relatively precise axial alignment of the optical fibers, it requires matching multi-channel test connector harnesses for each different type of optical connector 20 and is thus relatively expensive. In addition, the multi-channel test connector harness 28 is relatively difficult to maintain. For example, if one of the terminus gets dirty or is damaged, the entire multi-channel test connector harness 28 may have to be disassembled and replaced.
A third known method for testing the fiber-optic terminations is illustrated in FIG. 3. In this method an adapter 30 is utilized that is adapted to be coupled directly to the fiber-optic connector 20 to be tested. As shown in FIG. 3, the adapter 30 includes an alignment sleeve 32, which allows a terminus 34, carried by the fiber-optic connector 20 to be aligned with a terminus 36 of a fiber optic test probe 38. Even though the alignment sleeve 32 provides good axial alignment between the respective termini, the configuration allows for slight air gaps between the respective termini, which can result in reflections which in turn result in transmission losses. The air gap is caused by a lack of a biasing force to hold the two terminus ferrules together.